1. Field of the Invention
The present invention relates to a measuring apparatus utilizing attenuated total reflection (ATR), such as a surface plasmon resonance measuring apparatus for quantitatively analyzing a substance in a sample by utilizing the excitation of surface plasmon, and more particularly to a measuring apparatus, utilizing ATR, which can measure a large number of samples in a short time. The present invention also relates to a measuring apparatus that can measure a large number of samples in a short time.
2. Description of the Related Art
In metals, if free electrons are caused to vibrate in a group, a compression wave called a plasma wave will be generated. The compression wave, generated in the metal surface and quantized, is called surface plasmon.
There have hitherto been proposed various kinds of surface plasmon resonance measuring apparatuses for quantitatively analyzing a substance in a sample by taking advantage of a phenomenon that surface plasmon is excited by a light wave. Among such apparatuses, one employing a system called the xe2x80x9cKretschmann configurationxe2x80x9d is particularly well known (e.g., see Japanese Unexamined Patent Publication No. 6(1994) -167443).
The surface plasmon resonance measuring apparatus employing the xe2x80x9cKretschmann configurationxe2x80x9d is equipped with a dielectric block formed, for example, into the shape of a prism; a metal film, formed on one surface of the dielectric block, for placing a sample thereon; and a light source for emitting a light beam. The measuring apparatus is further equipped with an optical system for making the light beam enter the dielectric block so that a condition for total internal reflection (TIR) is satisfied at the interface between the dielectric block and the metal film and that various angles of incidence, including a surface plasmon resonance condition, are obtained; and photodetection means for measuring the intensity of the light beam totally reflected at the interface, and detecting surface plasmon resonance.
To obtain various angles of incidence in the aforementioned manner, a relatively thin light beam can be deflected so that it strikes the above-mentioned interface at different angles of incidence, or a relatively thick beam can be convergently emitted so that the components thereof strike the interface at various angles of incidence. In the former, the light beam whose reflection angle varies with the deflection thereof can be detected by a small photodetector that is moved in synchronization with the light beam deflection, or by an area sensor extending along a direction where the reflection angle varies. In the latter, on the other hand, the light beams reflected at various angles can be detected by an area sensor extending in a direction where all the reflected light beams are received.
In the surface plasmon resonance measuring apparatus mentioned above, an evanescent wave having electric field distribution is generated in a sample in contact with the metal film, if a light beam strikes the metal film at a specific incidence angle xcex8sp greater than a critical incidence angle at which total internal reflection (TIR) takes place. The generated evanescent wave excites surface plasmon at the interface between the metal film and the sample. When the wave vector of the evanescent wave is equal to the wave number of the surface plasmon and therefore the wave numbers between the two are matched, the evanescent wave resonates with the surface plasmon and the light energy is transferred to the surface plasmon, whereby the intensity of the light satisfying TIR at the interface between the dielectric block and the metal film drops sharply. This sharp intensity drop is generally detected as a dark line by the above-mentioned photodetection means.
Note that the above-mentioned resonance occurs only when an incident light beam is a p-polarized light beam. Therefore, in order to make the resonance occur, it is necessary that a light beam be p-polarized before it strikes the interface.
If the wave number of the surface plasmon is found from the specific incidence angle xcex8sp at which attenuated total reflection (ATR) takes place, the dielectric constant of a sample to be analyzed can be calculated by the following Equation:
Ksp(xcfx89)=(xcfx89/c){xcex5m(xcfx89)xcex5s}1/2/{xcex5m(xcfx89)+xcex5s}1/2 
where Ksp represents the wave number of the surface plasmon, xcfx89 represents the angular frequency of the surface plasmon, c represents the speed of light in vacuum, and xcex5m and xcex5s represent the dielectric constants of the metal and the sample, respectively.
If the dielectric constant xcex5s of a sample is found, the density of a specific substance in the sample is found based on a predetermined calibration curve, etc. As a result, the specific substance in the sample can be quantitatively analyzed by finding the specific incidence angle xcex8sp at which the intensity of the reflected light at the interface drops sharply.
As a similar sensor making use of ATR, there is known a leaky mode sensor (e.g., see xe2x80x9cSpectral Researches,xe2x80x9d Vol. 47, No. 1 (1998), pp. 21 to 23 and pp. 26 to 27). This leaky mode sensor is equipped with a dielectric block formed, for example, into the shape of a prism; a cladding layer formed on one surface of the dielectric block; and an optical waveguide layer, formed on the cladding layer, for placing a sample thereon. The leaky mode sensor is further equipped with a light source for emitting a light beam; an optical system for making the light beam enter the dielectric block at various angles of incidence so that a condition for total internal reflection (TIR) is satisfied at the interface between the dielectric block and the cladding layer and so that ATR occurs by a waveguide mode excited in the optical waveguide layer; and photodetection means for measuring the intensity of the light beam totally reflected at the interface between the dielectric block and the cladding layer, and detecting the excited state of the waveguide mode, that is, ATR.
In the leaky mode sensor mentioned above, if a light beam strikes the cladding layer through the dielectric block at incidence angles greater than a critical incidence angle at which TIR takes place, the light beam is transmitted through the cladding layer and then only light with a specific wave number, incident at a specific incidence angle, propagates through the optical waveguide layer in a waveguide mode. If the waveguide mode is excited in this manner, the greater part of the incident light is confined within the optical waveguide layer, and consequently, ATR occurs in which the intensity of light totally reflected at the above-mentioned interface drops sharply. Since the wave number of the light propagating through the optical waveguide layer depends on the refractive index of a sample on the optical waveguide layer, both the refractive index of the sample and the properties of the sample related to the refractive index thereof can be analyzed by finding the above-mentioned specific incidence angle xcex8sp at which ATR takes place.
In the field of pharmaceutical manufacture and the like, the above-mentioned surface plasmon resonance measuring apparatus and leaky mode measuring apparatus are sometimes used in a random screening method for detecting a specific substance that bonds with a predetermined sensing substance. In this case, the sensing substance is placed on the aforementioned thin film layer (i.e., the metal film in the case of the surface plasmon resonance measuring apparatus, or the cladding layer and optical waveguide layer in the case of the leaky mode sensor). Then, a liquid sample containing a target substance is dropped into the sensing substance, and each time a predetermined time elapses, the aforementioned specific incidence angle xcex8sp is measured.
If the target substance in the liquid sample bonds with the sensing substance, the refractive index of the sensing substance varies with the lapse of time by the bond therebetween. Therefore, every time a predetermined time elapses, the specific incidence angle xcex8sp is measured. Based on the measured value, the bond between the target substance and the sensing substance is measured. Next, based on the result, it can be judged whether or not the target substance is a specific substance that bonds with the sensing substance. An example of combination of the specific substance and the sensing substance is an antigen and an antibody. As an example of a measurement of such combination, there is a measurement of the bond between a human IgG (immunoglobulin G) antibody in a target substance and a rabbit antihuman IgG antibody (sensing substance).
Note that the specific incidence angle xcex8sp itself does not always need to be detected to measure the bond between the target substance and the sensing substance. For example, a liquid sample is added to the sensing substance; then a change in the specific incidence angle xcex8sp thereafter is measured; and based on the angle change, the bond can be measured.
However, a measuring apparatus, such as the aforementioned surface plasmon resonance sensor and leaky mode sensor, has the disadvantage that when measuring a plurality of samples, the measurement is extremely time-consuming. Particularly, in the case in which a single sample is measured several times at predetermined temporal intervals in order to detect a change in the properties of the sample due to an antigen-antibody reaction, a chemical reaction, etc., a new sample cannot be measured unless the measurement of the single sample is finished, and consequently, it takes too much time to measure all samples.
In view of the circumstances mentioned above, there has been proposed a measuring apparatus, utilizing ATR, which can measure a large number of samples in a short time (see Japanese Patent Application No. 2001-49681). In this measuring apparatus utilizing ATR, the aforementioned dielectric block, the thin film layer formed on one surface of the dielectric block (the metal film in the case of the surface plasmon resonance measuring apparatus, or the cladding layer and the optical waveguide layer in the case of the leaky mode measuring apparatus), and the sample holding mechanism for holding a sample on the thin film layer, are integrated into a measuring unit. The measuring apparatus is provided with a turntable and drive means for driving the turntable intermittently. The turntable is used for supporting a plurality of measuring units at predetermined intervals with respect to a rotation axis thereof. The measuring units on the turntable are serially stopped at a position where the aforementioned light beam is irradiated.
In the above-mentioned measuring apparatus utilizing ATR, when the irradiation of the light beam and the intensity detection of the totally reflected light are being performed on the measuring unit held at a predetermined position on the turntable being stopped, another process is simultaneously performed on another measuring unit held at another position. In this manner, the efficiency of the measuring operation is enhanced. Examples of the other process are the process of supplying a sample to a measuring unit, the process of pouring oil into the measuring unit with the sample to prevent evaporation of the sample, the process of removing the measuring unit for which measurements were made, from the turntable, the process of supplying a new measuring unit to the turntable, and so on.
In the above-mentioned measuring apparatus utilizing ATR, the samples held in the sample holding mechanisms of a plurality of measuring units can be serially measured by rotation of the turntable. Thus, according to the measuring apparatus, a large number of samples can be measured in a short time.
In addition, in the case where measuring units with a sample to be analyzed are generally employed in a measuring apparatus other than a measuring apparatus employing ATR, the measuring units are supported by a turntable, and each time the turntable is stopped, various processes are performed on the measuring unit. In this manner, as with the aforementioned case, the time required for measurements can be shortened. Such processes, in addition to the aforementioned processes, include the process of adding a reagent which reacts with a target substance and the process of agitating a sample, and, in a blood analyzer, etc., include the process of measuring the absorbance of a reagent that has reacted with a sample (such as blood, etc.) and the process of detecting the wavelength and intensity of fluorescent light emitted from the aforementioned reagent. The items to be inspected by the measurement include an enzyme related item, a nitrogen contained component, lipid, an electrolyte, sugar metabolism inspection, vital pigment inspection, kidney function inspection (e.g., detection of xcex11 micro-globulin in serum and urine, xcex22 micro-globulin in urine, albumin in urine, Tf in urine, IgG in urine, etc.), plasma protein inspection (e.g., detection of IgG, IgA, IgM, IgD, C3, C4, transferrin, etc.), tumor marker inspection (e.g., detection of BFP, xcex22 micro-globulin in blood, IAP, etc.), etc.
The present invention has been made in view of the circumstances mentioned above. Accordingly, it is the primary object of the present invention to provide a measuring apparatus, such as a measuring apparatus utilizing ATR, which is capable of efficiently performing processes on measuring units situated at predetermined positions on a turntable.
To achieve this end and in accordance with the present invention, there is provided a first measuring apparatus comprising:
n measuring units;
a turntable for supporting the n measuring units at intervals of a predetermined angle with respect to a rotation axis thereof; and
drive means for rotating the turntable intermittently at intervals of an angle equal to m times the predetermined angle (m is an integer);
wherein, when the turntable is stopped, k kinds of processes are respectively performed on the measuring units situated at different positions on the turntable;
and wherein the k is 2xe2x89xa6kxe2x89xa6n and the m is either 1, a number that is neither the common divisor of the n nor the common multiple, or a sum of 1 and the common multiple of the n.
In accordance with the present invention, there is provided a second measuring apparatus utilizing attenuated total reflection, comprising:
n measuring units comprising
a dielectric block, a thin film layer formed on one surface of the dielectric block, and a sample holding mechanism for holding a sample on the thin film layer;
a turntable for supporting the n measuring units at intervals of a predetermined angle with respect to a rotation axis thereof;
drive means for rotating the turntable intermittently at intervals of an angle equal to m times the predetermined angle (m is an integer);
a light source for emitting a light beam;
an optical system for making the light beam enter the dielectric block of the measuring unit, situated at a predetermined position when the turntable is stopped, at various angles of incidence so that a condition for total internal reflection is satisfied at an interface between the dielectric block and the metal film; and
photodetection means for measuring intensity of the light beam totally reflected at the interface to detect the attenuated total reflection;
wherein, when the turntable is stopped, k kinds of processes, including irradiation of the light beam and the detection of the intensity, are respectively performed on the measuring units situated at different positions on the turntable;
and wherein the k is 2 greater than kxe2x89xa6n and the m is either 1, a number that is neither the common divisor of the n nor the common multiple, or a sum of 1 and the common multiple of the n.
In accordance with the present invention, there is provided a third measuring apparatus utilizing attenuated total reflection, comprising:
n measuring units comprising
a dielectric block, a thin film layer, which comprises a metal film, formed on one surface of the dielectric block, and a sample holding mechanism for holding a sample on the thin film layer;
a turntable for supporting the n measuring units at intervals of a predetermined angle with respect to a rotation axis thereof;
drive means for rotating the turntable intermittently at intervals of an angle equal to m times the predetermined angle (m is an integer);
a light source for emitting a light beam;
an optical system for making the light beam enter the dielectric block of the measuring unit, situated at a predetermined position when the turntable is stopped, at various angles of incidence so that a condition for total internal reflection is satisfied at an interface between the dielectric block and the metal film; and
photodetection means for measuring intensity of the light beam totally reflected at the interface to detect the attenuated total reflection due to surface plasmon resonance;
wherein, when the turntable is stopped, k kinds of processes, including irradiation of the light beam and the detection of the intensity, are respectively performed on the measuring units situated at different positions on the turntable;
and wherein the k is 2xe2x89xa6kxe2x89xa6n and the m is either 1, a number that is neither the common divisor of the n nor the common multiple, or a sum of 1 and the common multiple of the n.
In accordance with the present invention, there is provided a fourth measuring apparatus utilizing attenuated total reflection, comprising:
n measuring units comprising
a dielectric block, a thin film layer, which comprises a cladding layer and an optical waveguide layer formed on the cladding layer, formed on one surface of the dielectric block, and a sample holding mechanism for holding a sample on the thin film layer;
a turntable for supporting the n measuring units at intervals of a predetermined angle with respect to a rotation axis thereof;
drive means for rotating the turntable intermittently at intervals of an angle equal to m times the predetermined angle (m is an integer);
a light source for emitting a light beam;
an optical system for making the light beam enter the dielectric block of the measuring unit, situated at a predetermined position when the turntable is stopped, at various angles of incidence so that a condition for total internal reflection is satisfied at an interface between the dielectric block and the cladding layer; and
photodetection means for measuring intensity of the light beam totally reflected at the interface to detect the attenuated total reflection due to a waveguide mode excited at the optical waveguide layer;
wherein, when the turntable is stopped, k kinds of processes, including irradiation of the light beam and the detection of the intensity, are respectively performed on the measuring units situated at different positions on the turntable;
and wherein the k is 2xe2x89xa6kxe2x89xa6n and the m is either 1, a number that is neither the common divisor of the n nor the common multiple, or a sum of 1 and the common multiple of the n.
Note that it may be difficult to describe the process in which an unused measuring unit is supplied to the turntable to be supported thereon as a xe2x80x9cprocess . . . performed on the measuring units situated at different positions on the turntablexe2x80x9d, because the measuring unit is situated on the turntable after this process is complete. However, in this specification, the measurement unit supply process is included as this type of process.
In addition, the k types of processes need not be performed on all of the measuring units situated at different positions on the turntable every time that the turntable is stopped. For example, when measurement is initiated, the first process is to supply a measuring unit to the turntable. Because there are no other measuring units on the turntable at this time, the other processes, such as supplying a sample to a measuring unit, irradiating of the light beam, and the detecting of the intensity are not performed.
The measuring apparatus of the present invention is equipped with the turntable and the drive means. The turntable is used for supporting n measuring units at intervals of a predetermined angle with respect to a rotation axis thereof. The drive means is used for rotating the turntable intermittently at intervals of an angle equal to m times the predetermined angle (m is an integer). When the turntable is stopped, k kinds of processes are respectively performed on the measuring units situated at different positions on the turntable. The above-mentioned k is 2xe2x89xa6kxe2x89xa6n, and the above-mentioned m is either 1, a number that is neither the common divisor of n nor the common multiple, or a sum of 1 and the common multiple of n.
With this arrangement, the n measuring units on the turntable can be fed in regular sequence, while avoiding the case in which before one measuring unit is fed once to sections in which the k kinds of processes are performed, another measuring unit is fed many times. That is, if the turntable is stopped n times, each of the n measuring units on the turntable is fed once to each processing section. Thus, the measuring apparatus of the present invention is capable of efficiently performing the above-mentioned k kinds of processes on each measuring unit.
The measuring apparatus, utilizing ATR, of the present invention is likewise able to obtain the same effect as the aforementioned effect.